Overload protection

ABSTRACT

An overload protection device in combination with a prime mover and gearbox transmission supplies torque through a gearbox transmission to a load. An input shaft with is driven by the prime mover and rotates therewith. An external spline on the input shaft mates with an input gear having an internal spline. Upon overload of the gearbox transmission, the input shaft fractures an annular groove in the input shaft. A bushing prevents travel of the portion of the input shaft which is driven by the prime mover and which continues to spin after the fracture.

FIELD OF THE INVENTION

The invention is in the field of overload protection for gearboxes usedto drive earth boring machines.

BACKGROUND OF THE INVENTION

A roadheader is an earth-boring machine which experiences high axial andradial loads on and in the frame of the machine. The roadheader includesa cutter head, a gearbox and a motor (prime mover). When the gearing,most notably the ring gear, is affixed to the housing of the gearbox,the axial and radial forces imparted on the cutter head are transmittedto the ring gear through the housing and cause misalignment of the gearsand other components. The misalignment causes abnormal gear wear andultimately destruction of the gears, carriers and other components.

Roadheaders operate in a range of motion with respect to horizontal. Inother words, the cutter head of the roadheader and the gearbox affixedthereto may be inclined with respect to horizontal and creatinglubrication problems with some of the bearings within the gearbox as thebearings are lifted out of the lubricating oil.

In the prior art, an internal tube requires internal connections whichpresent the potential for leaks. These leaks allow water to enter withinthe gearbox and cause it to fail. The potential for leaks is increaseddue to the extreme vibrations that exist within the gearbox as thecutter head cuts into soil and rock. The tube vibrates within thegearbox and the connections leak due to the vibrations.

U.S. Pat. No. 7,935,020 to Jansen et al. issued May 3, 2011, statesthat: “A drive train for a wind turbine is provided. The wind turbinecomprises a low speed shaft connected to blades of the wind turbine anda higher speed shaft connected to a generator. The drive train alsoincludes a bearing that substantially supports the weight of at leastthe low speed shaft. A compound planetary gear stage is connected to thelow speed shaft and the higher speed shaft, and includes a rotatingcarrier, a nonrotating ring gear, a plurality of planetary gears, and arotating sun gear. The sun gear is connected to the higher speed shaft.”

U.S. Pat. No. 4,873,894 to Avery et al. issued Oct. 17, 1989, states: “Abalanced free-planet drive mechanism includes a reaction ring gear, anoutput ring gear, an input sun gear arranged along a central axis, and aplurality of floating planet elements individually having a first planetgear engaged with the sun gear, a second planet gear engaged with theoutput ring gear, and a third planet gear engaged with the reaction ringgear. A required first rolling ring gear resists radially inwardmovement of the planet elements adjacent the third planet gear, and anoptional second rolling ring gear resists radially inward movement ofthe planet elements adjacent the first planet gears to maintain theplanetary elements essentially parallel to the central axis. A pluralityof ring segments are connected to the output ring gear and engage agroove in each of the planet elements to maintain the planet elements ina preselected axial position and to transmit relatively low thrustforces. The drive mechanism is easy to assemble in a ground-engagingwheel of a truck or the like, with the output ring gear being connectedto rotate with the wheel. The incorporation of the drive mechanism in awheel eliminates the usual planet carrier and planetary bearingsassociated with a conventional multi-stage planetary final drive, and islighter in weight and less costly while fitting compactly within thesame general space envelope.”

SUMMARY OF THE INVENTION

Floating Gearbox

When gears are under load, forces within a gear system align the gearsand other components of the gear system so that optimum load balancingoccurs, that is, the gears align themselves. External forces notgenerated by the gear system move the gears out of this alignment andthus adversely affect the gear position causing damage and prematurewear. The floating gear system of the invention allows gears to retaintheir most favorable alignment position.

An electric motor drives an input gears via spline connections. Theinput gear drives an intermediate gear. The intermediate gear drives theshaft which, in turn, drives the first sun gear such that theintermediate gear and the first sun gear rotate together at the samespeed. The first sun gear drives a set of first planet gears. Preferablythere are three first planet gears. The planet gears are engaged with astatic (fixed) ring gear. A first pair of spherical bearings isinterposed between each first planet gear and each first planet shaft.The first pair of spherical bearings is separated from each other andprovides support for the first planet gear. Each first planet shaft isaffixed to the first planetary carrier. The first planet gear forces thefirst planet carrier to rotate and thus drives second sun. Second sunincludes an external spline and a gear.

The second sun gear drives four second planet gears. The second planetgears engage static (rotationally fixed) ring gear. A second pair ofspherical bearings is interposed between each second planet gear andeach second planet shaft. The second pair of spherical bearings isseparated from each other and provides support for the second planetgear. Each second planet shaft is rotatably affixed to the secondplanetary carrier. The second planet gear forces the second planetcarrier to rotate and thus drive the output shaft.

The gears are allowed to float. Both vertical and horizontal forces acton the cutter head. These forces are transmitted through the gearbox andback to the supporting structure. In the present invention, the gearsrun independent of the housing, that is, they float. The ring gearfloats. The ring gear is spaced apart from the housing. A small annulargap exists between the ring gear and the housing, thus deflection due toexternal forces in the housing doesn't affect the gear alignment becausethe gears aren't directly attached to the housing. The ring gear hastorque passing through it and thus is anchored back (against rotation)to the housing through a spline connection between the ring gear and thecover. The cover is affixed to the housing and the spline connectionacts like a hinge. The ring gear and housing deflect independently ofeach other.

Spline connections in the present invention make the gears float.Splines have small gaps in them. These gaps allow small relativemovement between meshing splines and help the gears find a position thatbest suits them. The spline connections include the connection betweenring gear and cover; the second planet carrier and the output shaft; thefirst carrier and the second sun; and, the first sun gear and thesplined shaft, and, the intermediate gear and the splined shaft.

When gears are under load, the forces within the gear system align thegears so that optimum load balancing occurs, that is, the gears alignthemselves. In the prior art, external forces not generated by the gearsystem, move the gears out of alignment and thus adversely affect theirpositions. The present invention allows the planetary gear systems toretain their most favorable alignment positions.

A gearbox which includes a housing having a cover is disclosed. Thecover is affixed to the housing. The cover includes an external splinelocated on a central portion thereof. There are two input gears drivenby prime movers, for example, electric motors. The input gears drive anintermediate gear which is known as a drop down gear. The intermediate(drop down) gear includes an internal spline. The splined shaft includesa first external spline and a second exterior spline. The internalspline of the intermediate gear engages the first exterior spline of theshaft rotating the shaft with the intermediate gear. A centrally locatedtube resides along a first longitudinal axis of the housing. A centrallylocated adapter also resides along a first longitudinal axis of thehousing. The centrally located adapter is affixed to the housing. Thecentrally located adapter and centrally located tube are stationary.There are two spherical bearings, the shaft input spherical bearing andthe shaft output spherical bearing, which enable the components of thegearbox to float within the gearbox thus avoiding deformation andsubsequent destruction of the components. The components include thering gear, a splined shaft, a first planetary system, a second planetarysystem, and an output shaft. Each of the planetary systems includes asun gear, a plurality of planet gears, a planet gear carrier, and aplurality of planet gear shafts.

A first shaft input spherical bearing is interposed between thestationary tube and the rotating input shaft. A first sun gear includesan internal spline. The second external spline of the input splinedshaft engages the internal spline of the first sun gear driving the sungear therewith.

A plurality of first planet gears is carried by a first planet gearcarrier. Each planet gear is pinned to the first planet gear carrier bya first planet gear shaft. A first pair spherical bearings is interposedbetween each of the first planet gear shafts and each of the firstplanet gears. The first sun gear drives the first planet gears. Thefirst planet gear carrier restrains each of the first pair of sphericalbearings interposed between the first planet gear and the first planetgear shaft against longitudinal movement. The first planet gear carrierrestrains each of the first planet gears with respect to its respectivefirst planet gear shaft holding them against longitudinal movement intheir respective planet gear shaft. A ring gear is mounted within thehousing and includes an internal spline. The internal spline of the ringgear engages the external spline of the cover affixing the ring gearagainst rotation with respect to the cover/housing.

The plurality of first planet gears engages the ring gear driving thefirst planet carrier. The first planet carrier includes an internaloutput spline. A second sun includes an external spline and a sun gear.

The internal output spline of the first planet carrier drives theexternal spline of the second sun gear. The plurality of second planetgears engages the ring gear driving the second planet carrier. The gearof the second sun drives the second planet gears which, in turn, drivethe second planet carrier. The second planet gears engage the ring gear.A second pair of spherical bearings is interposed between the secondplanet gear shaft and the second planet gear. The second planet gearcarrier restrains the second pair of spherical bearings interposedbetween each of the second planet gears and the second planet gear shaftagainst longitudinal movement. The second planet gear carrier restrainsthe second planet gears with respect to its respective second planetgear shaft against longitudinal movement holding each of them againstlongitudinal movement. The second planet carrier includes an internaloutput spline.

The output shaft includes an external spline. The housing, the cover andthe output shaft have a longitudinal axis. The internal output spline ofthe second planet carrier drives the external spline of the outputshaft.

A shaft output spherical bearing resides intermediate the output shaftand the cover of the gearbox supporting the output shaft. The shaftoutput spherical bearing permits angular displacement of the outputshaft with respect to the longitudinal axis of the output shaft. Thering gear pivots with respect to the cover/housing. The shaft outputspherical bearing enables the ring gear to float within the housing andnot engage the housing.

A gearbox in combination with a roadheader is also disclosed. A primemover, a cutter head, a gearbox are disclosed. The gearbox includes: ahousing having an inner surface and an external spline; an input shaft;a first planetary gear system driven by the shaft; and, a secondplanetary gear system driven by the first planetary gear system. A ringgear includes an internal spline. A first pair of spherical bearingssupports the first planetary gear system. A second pair of sphericalbearings supports the second planetary gear system. The ring gearincludes an outer surface and the outer surface is substantiallycylindrically shaped. The outer surface of the ring gear is spaced apartfrom the inner surface of the housing forming an annular gaptherebetween. The internal spline of the ring gear engages the externalspline of the housing affixing the ring gear against rotation withrespect to the housing. The ring gear is pivotable with respect to thehousing. An output shaft is driven by the second planetary gear system.The gearbox is interposed between the prime mover and the cutter head.The prime mover delivers power to the input shaft of the gearbox and theoutput shaft of the gearbox drives the cutter head.

Lubrication

A bearing lubrication system is disclosed which includes a gearboxhousing wherein the gearbox housing includes a planetary gear system,the planetary gear system includes planet gears, an external spline, aninterior surface and an exterior surface. Lubricating oil resides in thegearbox housing and the planet gears pass through the lubricating oil inthe gearbox housing. The floating ring gear resides within the gearboxhousing and the floating ring gear is substantially cylindricallyshaped. The floating ring gear includes an inner portion and an outersurface. The inner portion of the floating ring gear includes aninternal spline and an internal gear. The internal spline of thefloating ring gear engages the external spline of the gearbox housingpreventing rotation of the floating ring gear with respect to thehousing. The exterior surface of the floating ring gear is radiallyspaced apart from the interior surface of the gearbox housing forming anannulus between the gearbox housing and the floating ring gear.

The planet gears of the planetary gear system engage the internal gearof the floating ring gear. The internal gear of the floating ring gearincludes a first passageway therein for receiving oil from the meshingof the planet gears with the internal gear of the floating ring gear.The first passageway extends through the floating ring gear. The outersurface of the floating ring gear includes first and second groovestherein. First and second O-rings reside in the first and second groovesof the outer surface of the O-rings and seal the annulus formed by thespace between the exterior surface of the ring gear and the interiorsurface of the housing. The gearbox housing includes a second passagewayin communication with the annulus. The second passageway in the gearboxhousing extends to the exterior surface of the housing. A cover affixedto the housing includes a third passageway in communication with thesecond passageway of the gearbox. The second passageway and the thirdpassageway are joined together at a joint and the joint is sealed withan O-ring.

The cover includes a void or cavity therein. The third passagewaycommunicates between the joint and the void in the cover. The coverincludes a fourth passageway and a circumferential recess. The fourthpassageway communicates between the void in the cover and thecircumferential recess in the cover. The shaft output spherical bearingis mounted adjacent the circumferential recess in the cover. Thelubricating oil is forced and pumped into and through the firstpassageway through the floating ring gear and into the annulus betweenthe gearbox housing and the floating ring gear. Lubricating oil from theannulus is pumped into and through the second passageway and through thejoint between the second and third passageway. Then the oil is pumpedthrough the third passageway into the void/cavity in the cover.Thereafter the oil passes through the fourth passageway between the voidin the cover and the circumferential recess in the cover and lubricatingthe shaft output spherical bearing mounted adjacent the recess.

A bearing lubrication system is disclosed which includes a gearboxhousing wherein the gearbox housing includes a planetary gear system,the planetary gear system includes planet gears, an external spline, aninterior surface and an exterior surface. The gearbox includes an outputshaft and the shaft output spherical bearing is interposed between theoutput shaft and the cover. Lubricating oil collects in the void and thegearbox tilts at an angle up to 43° with respect to horizontal duringoperation. A floating ring gear resides within the gearbox housing andis substantially cylindrically shaped. The floating ring gear includesan inner portion and an outer surface. The inner portion of the floatingring gear includes an internal gear. The floating ring gear engages thegearbox housing preventing rotation of the floating ring gear withrespect to said housing. The exterior surface of said floating ring gearis radially spaced apart from the interior surface of the gearboxhousing forming an annulus between the gearbox housing and the floatingring gear. The planet gears of the planetary gear system engage theinternal gear of the floating ring gear. The internal gear of thefloating ring gear meshes with the planet gears pumping oil through thefloating ring gear, the annulus, the gear box housing, the cover and theshaft output spherical bearing.

The shaft output spherical bearing which resides between thecover/housing and the output shaft has oil pumped to it to ensure thatit is lubricated at all times. When the cutter head resides horizontallywith respect to the earth, oil is supplied to the shaft output sphericalbearing by virtue of the oil within the housing. At this time the shaftoutput spherical bearing also receives oil from the pumping system ofthe invention. The cutter head, and thus the gearbox, can tiltsubstantially with respect to the horizontal axis of the gearbox. Theshaft output spherical bearing when inclined is lifted up out of the oilresiding in the housing. Oil, or other lubricant, normally fills thehousing up to the 50% level based on height. A sight glass is providedin the window which enables the roadheader user to view the oil level inthe gearbox. Ring gear and surrounding pieces act, in addition to theirnormal function, like a pump. In the ring gear, just above the firstplanet gears, there are three small holes between the teeth of the ringgear. The three holes are spaced 120° apart. As the gear teeth of thefirst planet gears and the ring gear mesh (engage), oil is forced upinto these holes. Oil will then flow to and then through the narrowcavity that is between the ring gear and the housing. O-rings at theends of the ring gear keep the oil from leaving the volume bounded bythe exterior surface of the ring gear and the internal surface of thehousing. Oil is then forced though passageways and cavities in thehousing and cover so that oil reaches the shaft output sphericalbearing, and thus keeps the shaft output spherical bearing lubricated.

The gearbox of the invention is large and deep holes in the housing fora lubrication system are costly and difficult to manufacture. Instead,the invention obviates the need for deep holes. The gap between the ringgear and the housing is adapted to transport oil. Both ends of the ringgear are sealed with the O-rings. This gap provides an oil passage forthe majority of the distance—the distance up to the front of thegearbox. The first planet gear pumps the oil used for lubricating theshaft output spherical bearing instead of the second planet gear becausethe first planet gear rotates much faster than the second planet gearand therefore makes a much more effective pump. After the gap, oilpasses through some relatively short length passageways and thereafterfalls into a cast cavity/void in the cover. This cast cavity is used inthe lubrication system and obviates deep holes. After the cast cavity,oil passes through another short passageway and reaches the shaft outputspherical bearing.

Overload Protection

The gearbox has over-torque protection. The input shaft includes anarrowed diametrical portion which acts as a fuse. In the prior art, ifexcessive force is applied to the cutter head an internal gear componentfails. The input shaft acts as a fuse and breaks at the narroweddiametrical portion. When the fuse breaks, the portion of the shaft thatis still connected to the electric motor spins harmlessly within abushing. The bushing prevents the spinning portion of the input shaftfrom entering the bore in the gear too far. A screw retains the portionof the shaft bearing the external spline. The internal spline of thebore in the input gear remains meshed together with the external splineof the shaft after breakage or fracture of the shaft. This over-torqueprotection system prevents damage to the ring gear as well as tocomponents of the rest of the gearbox. The two broken portions of theinput shaft can easily be replaced.

To prevent damage to the input gear while the outer half of the inputshaft is spinning, a bushing permits spinning to occur in a controlledfashion and thus prevent damage to the input gear. In other words, thebushing acts as a shoulder and prevents the input shaft from movinginwardly toward the input gear thus damaging the gear. When the fuse isnot broken and the gearbox is running in a normal, proper fashion, thebushing sees no rotation and it radially supports the input shaft. Thebushing only functions when the fuse breaks. If any damage occurs to theO-ring when the fuse breaks, it can be easily replaced. The function ofthe O-rings along the input shaft is to retain grease at the bushing andthe spline. The input shaft includes an external spline which mates withan internal spline on the input gear.

An overload protection device in combination with a prime mover andgearbox transmission supplying torque through said gearbox transmissionto a load is disclosed. An input shaft includes a bore therethroughenabling affixation of the input shaft to an input gear. The input shaftincludes a key for coupling to the prime mover and for rotationtherewith. The input shaft also includes an external spline which mateswith an internal spline in the bore of the input gear. The prime movertransmits torque to the input shaft which drives the input gear. Theinput gear includes a bore therein. An internal spline in the bore ofthe input gear meshes with the external spline of the input shaft. Thebore of the input gear includes a shoulder therein, and the bushingresides in the bore of the gear and engages the shoulder of the bore.The input gear of the gearbox transmission drives a planetary gearsystem which, in turn, supplies power to the load.

The input shaft includes an annular groove which breaks when the loadimpressed upon the cutting tool of the roadheader is too large. Uponoverload of the gearbox transmission, the input shaft breaks at thelocation of the annular groove. The input shaft includes a bore thereinand the annular groove in combination with the bore through the shaftresults in a thin section which acts as a fuse. The input shaft isaffixed to the input gear against longitudinal movement such that theinput shaft will not move longitudinally after the input shaft breaks.

Cooling Cavities

A gearbox, comprising: a housing and a floating gear means forprotecting a gear mechanism from damage due to axial and radial forcesapplied to the gearbox is disclosed. A first cooling compartment and asecond cooling compartment are disclosed. The first and second coolingcompartments are isolated from the floating gear means. First and secondports supply cooling fluid to the first compartment, and, the third andfourth ports supplying cooling fluid to the second compartment.

It is not possible for cooling water to leak into the gearbox as thegearboxes are sealed with respect to the cooling compartments. Instead,any water leakage falls harmlessly to the ground. Water in thecavities/compartments is isolated from the gearbox by a thick, heatconductible, wall of steel. Cooling cavities/compartments exists at eachend of the gearbox, behind the rear plate and the front plate. Plugs areremoved from threaded holes, and hoses are attached to the threadedholes for pumping cooling water into and through thecavities/compartments. The cooling water in the cavities soaks up heatgenerated in the gearbox.

There is a tube that passes through the central portion of the gearbox.When the gearbox is installed in an earth-boring machine, a pipecarrying cooling fluid is installed which passes through this tube andfeeds water to the cutter head.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a roadheader including the cutter head,gearbox and prime mover.

FIG. 1A is an enlarged portion of the schematic view of FIG. 1illustrating the cutter head and gearbox.

FIG. 1B is a perspective view of the gearbox.

FIG. 1C is a front view of the gearbox.

FIG. 1D is a right side view of the gearbox where power is input to thegearbox.

FIG. 1E is a left side view of the gearbox where power is output fromthe gearbox.

FIG. 1F is a cross-sectional view taken along the lines 1F-1F of FIG. 1Dillustrating the first planetary gear system, the second planetary gearsystem, the floating ring gear, the input to the first planetary gearsystem, and the output from the second planetary gear system, all ofwhich are supported by the shaft input and output spherical bearings andconnected with splines enabling the gear systems and ring gear to floatwithin a fixed housing.

FIG. 1G is an enlarged portion of the cross-sectional view of FIG. 1Fillustrating the floating ring gear, the spline connection between thefloating ring gear and the cover, and a portion of the lubricationsystem.

FIG. 1H is an enlarged portion of the cross-sectional view of FIG. 1Fillustrating the spline input to the first sun driving the firstplanetary gear set, the first planet carrier driving the second sun, thesecond sun driving the second planetary gear set and the second planetcarrier driving the output spindle (shaft), all of which are supportedby shaft input spherical bearing and the shaft output spherical bearingenabling the gear systems and ring gear to float within a fixed housing.

FIG. 1I is an enlarged portion of the cross-sectional view of FIG. 1Fillustrating the shaft input spherical bearing interposed between thecentrally located support tube and the splined shaft driven by theintermediate gear.

FIG. 1J is a perspective view of the floating gearbox without the ringgear and without the housing.

FIG. 1K is a perspective view of the floating gearbox with the ring gearshown in an exploded position. FIG. 1L is a diagrammatic view of anangular spline.

FIG. 1M is a diagrammatic view of an involute spline.

FIG. 2 is a cross-sectional view taken along the lines 2-2 of FIG. 1Dillustrating the fused input shaft with a splined connection to theinput gear which drives the intermediate gear which in turn drives thesplined shaft.

FIG. 2A is a front view of the input gear.

FIG. 2B is a cross-sectional view of the input gear illustrating theinternal spline for connection with the fused input shaft.

FIG. 2C is a front view of the fused input shaft.

FIG. 3 is a cross-sectional view taken along the lines 3-3 of FIG. 1Eillustrating the lubrication system and passageways in the ring gear,the housing, and the cover.

FIG. 3A an enlargement of a portion of FIG. 3 illustrating the lubricantpassages through the cover and housing.

FIG. 3B is a perspective view of a portion of the cover illustrating thelubricant pathway therethrough.

FIG. 3C is a plan view of the floating ring gear illustrating one of thelubricant passageways therethrough.

FIG. 3D is a cross-sectional view of the floating ring gear illustratingthe lubricant passageway therethrough, the housing, the meshing gear andthe gap between the ring gear and the housing.

FIG. 4 is a top view of the gearbox illustrating cooling water plugs.

FIG. 4A is a right end view of the gearbox with the cooling water plateremoved illustrating the water cavity, the water inlet, the wateroutlet, and a wall separating the water cavity from the gear systems.

FIG. 4B is the left end view of the gearbox with the cooling water plateremoved illustrating the water cavity, the water inlet, the wateroutlet, and a wall separating the water cavity from the gear systems.

DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic view 100 of a roadheader 7R including the cutterhead 3, gearbox 9 and prime mover 7. FIG. 1A is an enlarged portion 100Aof the schematic view of FIG. 1 illustrating the cutter head 3 andgearbox 9 in more detail. As illustrated in FIGS. 1 and 1A, electricmotors 7 drive input gears 2B which in turn drive, via splineconnections, input gears 2A. Input gears 2A drive intermediate gear 3A.

Still referring to FIGS. 1 and 1A, a horizontal or axial force 4 isimparted on the cutter head 3 in earth boring operations. The roadheader(earth boring machine) is forced into earthen material which may be veryhard. The cutter head 3 includes spikes thereon (not shown) whichforcibly cut into the earthen material. All of the axial forces 4 aretransmitted through the frame of the cutter head 3, the coupling frame6A, the housing 1 of the gearbox 9, the cover 2 of the gearbox 9, andthe motor frame 7A. Similarly, the cutter head is subject to radialforce 5 as illustrated in FIGS. 1 and 1A. All of the radial forces aretransmitted through the frame of the cutter head 3, the coupling frame6A, the housing 1 of the gearbox 9, the cover 2 of the gearbox 9, andthe motor frame 7A. The vertical and horizontal forces are nottransmitted to the ring gear, and, therefore, not transmitted to thefirst and second planetary gear systems. The planetary gear systemswithin the gearbox are supported by a shaft input spherical bearing anda shaft output spherical bearing enabling the planetary gear systems tofloat, that is, to self-center and align and to avoid deformation andmisalignment caused by forces normally transmitted (in the prior art) tothe gear systems by the frame of the gearbox. The shaft input and outputspherical bearings, a plurality of meshing internal and externalsplines, and a plurality of meshing gears permit the planetary gearsystems to float, that is, to self-center and align. Tolerance stack upof the components, namely, the various gears, splines, carriers etc.cause the components of a gearbox to find a natural orientation andalignment within the gearbox.

The gears are allowed to float. Vertical and horizontal forces act onthe cutter head. These forces are transmitted through the gearbox andback to the supporting structure. In the prior art, the ring gear isfixed to the housing and forces transmitted to the housing causemisalignment of the ring gear and other components of the planetary gearsystem. This misalignment will cause abnormal alignment, gear wear anddamage to the planetary gear system.

In the instant invention the gears run independent of the housing; thatis, they float. Ring gear 22 floats as it is separate from the housing1. A small annular gap 22G exists between the ring gear 22 and housing1, and, thus forces in the housing 1 do not affect alignment of thegears within the housing.

The ring gear 22 has torque passing through it and is anchored to thehousing 1. This is done through a spline connection 59, 60 between thering gear 22 and the cover 2 which acts like a hinge and pivots asindicated by reference numeral 99. Cover 2 is affixed to housing 1. Ringgear 22 and housing 1 deflect independently of each other.

Still referring to FIGS. 1 and 1A, the drive shaft 6A in the roadheaderis coupled to the output shaft 28 through a coupling 6B. Coupling 6Bfurther isolates and prevents any force from transmission to the outputshaft 28. Coupling 8 couples the input of the electric motor to theinput shaft 2B. Channel 6C functions as a water conduit through theroadheader to cool the cutter head 3 during operation.

FIG. 1B is a perspective view 100B of the gearbox 9 illustrating inputshafts 2B, 2B and bearing retention plates 10, 10. Housing 1, cover 2and an unnumbered sight glass are illustrated in FIG. 1B. Receptacles2R, 2R of input gears 2A, 2A receive input shafts 2B, 2B.

Referring to FIGS. 1B and 1F, adapter 13 is bolted to housing 1 withscrews 13A as illustrated in FIG. 1F. Further, the rear cooler cap 12 isbolted to housing 1 with screws 12S. Front cooler cap 25 is affixed tothe cover 2 as illustrated in FIG. 1E by screws 11. Tube 21 is affixedto adapter against rotation by dowel pin 26 as illustrated in FIGS. 1Fand 11.

FIG. 1E is a left side view 100E of the gearbox 9 where power is outputfrom the gearbox 9 by output shaft 28 and through spline connection 28S.FIG. 1E further illustrates bearing cover 30, retainer 36, and tube 21.

Referring to FIGS. 1E and 1F, bearing cover 30 is affixed to the cover 2by screws 30S and retains the shaft output spherical bearing 27. Dowelpins 41 are used to correctly orient the cover 2 with respectivereceptacles in housing 1. Screws 2X secure the cover 2 to the housing 1.Lip seal 31 is interposed between bearing cover 30 and output shaft 28.

Referring to FIGS. 1F and 1H, the shaft output spherical bearing 27includes an inner race 27I, and outer race 27O, and rollers 27R. Shaftoutput spherical bearing 27 is interposed between output shaft 28 andcover 2 and is longitudinally held in place by bearing cover 30, ashoulder 28L on shaft 28, and a shoulder 2S of cover 2. Tube 21 isstationary and affixed to adapter 13 proximate the rear end of thegearbox by dowel 26 and is supported by retainer 36 proximate the frontend of the gearbox 9. Retainer 36 is affixed to output shaft 28 by ascrew in a different plane which is not shown. Retainer 36 rotates withoutput shaft 28.

Referring to FIG. 1F, bearing 34 is interposed between tube 21 andretainer 36 enabling rotation of the retainer 36 while supporting secondplanet carrier 5A. Lip seal 33 is interposed between retainer 36 andtube 21 retaining lubricant for bearing 34 and other components.Retainer 36 retains shaft 28 from extraction. O-ring 61 is retainedaxially between shaft output spherical bearing 27 and second planetcarrier 5A.

FIG. 1C is a front view 100C of the gearbox 9 illustrating most of thesame principal elements illustrated in FIG. 1B. FIG. 1C illustratesoutput shaft 28 having an external spline 28S for mating with coupling6B. FIG. 1C further illustrates bearing cover 30 for retention of shaftoutput spherical bearing 27 which supports output shaft 28 asillustrated in FIG. 1F. Cooling cover plate 12 is also illustrated inFIG. 1D.

FIG. 1D is a right side view 100D of the gearbox 9 where power is inputto the gearbox 9 via input shafts 2B. Receptacles 2R receive the inputshafts 2B which are keyed. Bearing covers 10 retain bearings asillustrated in FIG. 2. Input shafts 2B include external splines 2P whichmesh with internal splines 2I in receptacles 2R. FIG. 3 is across-sectional view taken along the lines 3-3 of FIG. 1E illustratingthe input shaft 2B and the input gear 2A.

FIG. 1F is a cross-sectional view 100F taken along the lines 1F-1F ofFIG. 1D illustrating the first planetary gear system, the secondplanetary gear system, the floating ring gear 22, the input to the firstplanetary gear system, and the output from the second planetary gearsystem 28, all of which are supported by shaft input and outputspherical bearings and connected with splines enabling the gear systemsand ring gear to float within the fixed housing. A pair of firstspherical bearings 4C, 4C is interposed between the first planet gears4B and the first planet shaft 4D supporting the first planet gears 4Bwith respect to first planet shaft 4D. A pair of second sphericalbearings 5C, 5C is interposed between the second planet gears 5B and thesecond planet shaft 5D supporting the second planet gears 5D withrespect to first planet shaft 5D. Shaft input spherical bearing 3C isinterposed between tube 21 and splined shaft 3B supporting the splinedshaft with respect to the tube 21. Tube 21 is affixed to adapter 13, andadapter is affixed to the housing 1. Seal 14 is an O-ring sealinterposed between the adapter and the housing 1. Shaft output sphericalbearing 27 is interposed between the cover 2 and the output shaft 28supporting said output shaft with respect to the cover 2. Cover 2 isaffixed to housing 1 by screws 2X shown in FIG. 1E.

Referring to FIGS. 1F and 1G, each of the pair of spherical bearings 5Cincludes an inner race 71, outer race 73, and rollers 72. Referring toFIGS. 1F and 1I, shaft input spherical bearing 3C includes inner race77, outer race 79, and rollers 78. Referring to FIGS. 1F and 1H, each ofthe pair of spherical bearings 4C includes inner race 74, outer race 76,and rollers 75.

FIG. 1G is an enlarged portion 1000 of the cross-sectional view of FIG.1F illustrating the floating ring gear 22, the spline connection 59, 60between the floating ring gear 22 and the cover 2, and a portion of thelubrication system. Referring to FIG. 1F and 1G, cover 2 includes anexternal spline 59 and ring gear 22 includes an internal spline 60.External spline 59 loosely engages internal spline 60 permitting ringgear 22 to pivot with respect to external spline 59. Ring gear 22 doesnot rotate with respect to cover 2. However, ring gear 22 may pivot orrotate slightly as indicated by arrow 99. Gap 22G is an annular gapbetween the interior surface of the housing 1 and the exterior surface22Z of the ring gear 22. The ring gear is viewable in FIGS. 3B and 3C.

Referring to FIGS. 1F and 1G, ring gear 20 includes teeth 57 which meshwith teeth 58 of the second planet gears 5B, and, ring gear 20 includesteeth 56 which mesh with teeth 55 of the first planet gears 4B. Althoughthe teeth mesh as described, there is sufficient play between the teethto permit the relative rotational movement between the ring gear 20 andthe planet gears so as to enable ring gear 20 to pivot as indicated byreference numeral 99. The amount of pivoting or rotation of the ringgear will, of course, depend on the size of the annular gap 22G.Further, there may be relative rotational movement between the planetgears 4B, 5B and the internal ring gear 20 depending upon the dynamicsand loading of the planetary gear systems within the gearbox. FIG. 1H isan enlarged portion 100H of the cross-sectional view of FIG. 1Fillustrating the spline shaft 3B input to the first sun 3E driving thefirst planetary gear set 4B, the first planet carrier 4A driving thesecond sun 20, the second sun 20 driving the second planetary gear set5B and the second planet carrier 5A driving the floating output spindle28, all of which are supported by shaft input and output sphericalbearings 3C, 27 enabling the gear sets, carriers, suns and ring gear tofloat within a fixed housing 1.

Referring to FIGS. 1F and 1H, second sun 20 includes a first externalgear 69 having teeth 69A and an external spline 68. External spline 68of second sun 20 meshes with internal spline 67 of first planet carrier4A. Teeth 69A of second sun gear 69 mesh with teeth 70 of planet gear5B. Further, second carrier 5A includes an internal spline 66 whichmeshes with external spline 65 of output shaft 28. Internal spline 66meshes with external spline 65 and there may be some relative rotationalmovement between the meshed splines. Although the teeth and spline meshas described, there is sufficient play between the teeth to permit therelative rotational movement between the second sun 20, the firstcarrier 4A, and the second planet gears 5B so as to enable pivoting asindicated by reference numeral 99A.

Still referring to FIGS. 1F and 1H, second carrier 5A includes aninternal spline 66 and output shaft 28 includes external spline 65.Internal spline 66 meshes with output spline 65. Although the splinemeshes as described, there is sufficient play between and in the splineconnection to permit relative rotational movement between the second sun20, the first carrier 4A, and the second planet gears 5B so as to enablepivoting as indicated by reference numeral 99A.

FIG. 1I is an enlarged portion 1001 of the cross-sectional view of FIG.1F illustrating shaft input spherical bearing 3C interposed between thecentrally located support tube 21 and the splined shaft 3B driven by theintermediate gear 3A. FIG. 1I illustrates retaining rings 3F holdingfirst sun gear 3A in place. Shaft input spherical bearing 3C ispositioned between the adaptor 13 and a shoulder on tube 21.Additionally, bearing 3C is positioned between the spline shaft 3B andthe retaining rings residing partially in a groove of the splined shaft3B. Referring to FIGS. 1F, 1H, and 1I, splined shaft 3B includesexternal spline 53 meshing with internal spline 54 of intermediate gear3A. Splined shaft 3B includes external spline 51 meshing with internalspline 52 of sun 3E. Although the spline meshes as described, there issufficient play therebetween to permit the relative rotational movementbetween the splined shaft 3E, first sun 3E, and intermediate gear 3A soas to enable pivoting as indicated by reference numerals 99B and 99C.FIG. 1J is a perspective view 100J of the floating gearbox without thering gear 20 and without the housing 1 shown. FIG. 1K is a perspectiveview 100K of the floating gearbox with the ring gear 20 shown in anexploded position and without the input gears shown. Passageway 22Z isfor lubricant to flow from the interior side of the ring gear and, morespecifically, from the interior teeth 56 to the outer surface 22S. Thereare three passageways 22P in the ring gear. Also illustrated well inFIG. 1K is the interior gear 58 of the ring gear 22 and the internalspline 60. Internal spline 60 meshes with the external spline 59 ofcover 2. Cover 2 is fixed to the housing 1 and prevents rotation of thering gear 22 with respect to cover 2 and housing 1.

Referring to FIG. 1J, the input drive shafts 2B drive input gears 2Awhich, in turn, drive intermediate gear 3A. Intermediate gear 3Aincludes an internal spline 53 meshed with spline 54 of shaft 3B suchthat spline shaft 3B rotates with intermediate gear 3A. Input gears 2Ainclude teeth 84 which mesh with teeth 85 of intermediate gear 3A.

The first planetary gear system illustrated in FIGS. 1F, 1J and 1Kincludes a plurality of planet gears 4B, a first planet carrier 4A, and,a first sun gear 3E. Preferably there are three planet gears 4B and theyare retained in place by shaft retainers 17. The second planetary gearsystem illustrated in FIGS. 1F, 1J and 1K includes a plurality of planetgears 5B, a second planet carrier 5A, and a second sun 20. Preferablythere are four planet gears 5B and they are retained in place by shaftretainers 17. Second sun 30 is self-centering and is spaced about tube20. Washers 20R, 20L position second sun 20 between retainer 36 andspline shaft 3B.

FIG. 1L is a diagrammatic view 100L of an angular internal spline and anangular external spline with vertical gaps 95A, 96A between the internaland external spline teeth. Further, FIG. 1L illustrates a horizontal gap97A between the internal and external spline teeth. Sometimes horizontalgap 97A is called the backlash between the teeth of the mated spline. SWis the space width and TT is the tooth thickness as used in FIGS. 1L and1M.

FIG. 1M is a diagrammatic view 100M similar to FIG. 1L using an involutespline tooth profile with vertical spline gaps 95I, 96I between theinvolute internal and external spline teeth. Further, FIG. 1Millustrates a horizontal gap 97I between the involute internal andexternal spline teeth. Sometimes horizontal gap 97I is called thebacklash between the teeth of the mated spline.

The gaps just described and illustrated are demonstrative of all of thespline interconnections described herein and enable relative rotationalmovement between components. Relative rotational movement also occursbetween gears. For instance, rotational movement may take place betweenring gear 22 and cover 2, second planet gear 5B and ring gear 22, secondplanet gear 5B and second sun 20, second planet carrier 5A and outputshaft 28, first planet gear 4B and ring gear 22, first planet gear 4Band first sun gear 3E, first planet carrier 4A and second sun 20, firstsun gear 3E and splined shaft 3B, and, intermediate gear 3A and splinedshaft 3B.

FIG. 2 is a cross-sectional view 200 taken along the lines 2-2 of FIG.1D illustrating the fused input shaft 2B with a splined connection 2I,2P to the input gear 2A which drives the intermediate gear 3A.Intermediate gear 3A includes an internal spline 54 which is meshed withexternal spine 53 of spline shaft 3B. Splined shaft 3B rotates withintermediate gear 3A. Still referring to FIG. 2, input gear 2A issupported by cylindrical bearings 48, 49 in housing 1. Seal 40 residesbetween bearing cover 10 and receptacle 2R. Bearing cover 10 and inputgear shoulder 48S secure cylindrical bearing 48 in place between thehousing and the input gear. Housing shoulder 49S and shoulder 49B ininput gear 2A secure cylindrical bearing 49 in place between the housing1 and the input gear 2A. FIG. 2A is a front view 200A of the input gear2A illustrating gear teeth 84 and the receptacle portion 2R. FIG. 2B isa cross-sectional view 200B of the input gear 2A illustrating theinternal spline 2I for connection with the fused input shaft. FIG. 2C isa front view 200C of the fused input shaft 2B illustrating a fuseportion 82F, an external spline 2P, an outer shaft portion 82C, an innershaft portion 82D, and a stepped bore 81 therethrough. A keyway 82K isillustrated in the shaft portion 82C. Keyway 82K mates with acorresponding key of the coupling 8 which transfers power from theelectric drive motor 7 to the input shaft 2B.

Gearbox 9 has over-torque protection. Input shaft 2B includes adiametrically reduced portion 82F. The shaft thickness in the region 82Rbetween the stepped bore 81 and the diametrically reduced portion 82F isconsiderably smaller than in other shaft locations 82C, 82D. O-rings 2E,2G seal input shaft 2B against the unwanted intrusion of dirt and forthe retention of grease between the seals. Should excessive force beapplied to the cutter head 3, input shaft 2B functions as a fuse andfractures at the diametrically reduced portion 82F. When this fractureoccurs, a portion of input shaft 2B is still connected to the coupling 8and spins harmlessly within bushing 2C.

Input gear 2A includes a stepped bore 86 having a first shoulder 86A anda second shoulder 86B therein. Bushing 2C resides in the bore 86 of thereceptacle 2R and engages second shoulder 86B therein. Input shaft 2Bincludes outer shoulder 82H thereon. Outer shoulder 82H of input shaft2B engages first shoulder 86A in the bore 86 of receptacle 2R when thefuse 82F breaks. It will be noticed that outer shoulder 82H includes achamfer 82Z which matches a corresponding surface on first shoulder 86Aof bore 86 of receptacle 2R. In the normal condition without the fusebroken, outer shoulder 82H does not engage first shoulder 86A in thebore 86. Bore 81 of the input shaft 2A is a stepped bore which includesa first shoulder 81A and a second shoulder 81B.

Bushing 2C and shoulders 86A, 86B in bore 86 of receptacle portion 2R ofinput gear 2A prevent the diametrically reduced portion 82F (oncebroken) from moving inwardly toward the central portion of gear 2Apreventing damage to gear 2A and/or the internal spline 2I of thereceptacle portion 2R of gear 2A. Screw 2F retains the inner portion 82Dof the shaft 2B within the receptacle portion 2R of input gear 2A. Thisover-torque protection system prevents damage occurring to ring gear 2Aas well as to the other components of the gearbox. The two broken shaftportions 82C, 82D of shaft 2B are easily replaced.

To prevent damage to gear 2A while the outer fuse half is spinning,bushing 2C permits spinning to occur in a controlled fashion and thusprevents damage to the receptacle 2R of gear 2A. When fuse 82F is notbroken and the gearbox is running in a normal, proper fashion, bushing2C supports shaft 2B. Bushing 2C only functions when fuse 82F breaks oropens. If any damage occurs to the O-ring 2G when fuse 2C breaks, it canbe easily replaced. The function of the O-rings 2G, 2E is to retaingrease at the bushing 2C and the spline 2P. FIG. 3 is a cross-sectionalview 300 taken along the lines 3-3 of FIG. 1E illustrating thelubrication system and passageways in the ring gear 22, the housing 1,and the cover 2. FIG. 3A is an enlargement 300A of a portion of FIG. 3illustrating the lubricant passageways through the cover 2. Gap 22G isformed as an annulus between ring gear 22 and the interior surface ofhousing 1. The geometry of gap 22G changes with operation of thegearbox, that is, with the pivoting action of the ring gear 22 withrespect to cover 2.

FIG. 3B is a perspective view 300B of a portion of the cover 2illustrating the lubricant pathway therethrough by the unnumberedarrows. The arrows with dashed lines indicate the lubricant flow withinand through cover 2.

FIG. 3C is a plan view 300C of the floating ring gear 22 illustratingthe lubricant passageway 22P therethrough. FIG. 1K illustrates 3 oilpassageways 22P which are separated 120° apart meaning that at least twopassageways 22P may be oriented below the oil line if the housing 1 isfilled half full of lubricant. FIG. 3D is a cross-sectional view 300C ofthe floating ring gear 22 illustrating the lubricant passageway 22P,housing 1, and annular gap 22G between the ring gear and the housing 1.Planet gear 4B is illustrated meshed with ring gear 4B wherein pumpingaction of the planet gear forces lubricant into and through passageway22P.

The cutter head 3, and thus the gearbox 9, can tilt up to a maximum of43° 22′ with respect to horizontal as illustrated by arrow 99Z inFIG. 1. The tilt in a downward arc may occur to a minor extent but itwill not affect bearing lubrication When gearbox 9 is tilted up it willlifted out of the lubricant (oil). This in turn will cause the bearingto overheat, scorch, and then fail. Ring gear 22 and surrounding pieces,in addition to their normal function, function as an oil pump. In thering gear 22, just above planet gear 4B is a small passageway betweenthe teeth of the ring gear. As the gear teeth mesh, lubricating oil isforced up into this passageway 22P. First planet gears 4B were chosen topump oil instead of second planet gears 5B because planet gears 4B spinmuch faster than second planet gears 5B and therefore make a much moreeffective pump. Lubricating oil then flows to and then through theannulus 22G that is between the ring gear 22 and the housing 1. O-rings24 at each end of the ring gear keeps the lubricant under pressure fromspilling out. Lubricating oil is then forced though a series ofpassageways of holes and cavities so that oil reaches shaft outputbearing 27, and thus keeps the shaft output bearing 27 lubricated.

Referring to FIGS. 1G, 3 and 3A, lubricant is pumped by gear teeth 55 offirst planetary gears 4B through passageways 22P. There are threepassageways 22P spaced 120° apart as illustrated in FIG. 1K. Thelubricant exits passageways 22P supplying a volume as defined bygenerally annularly shaped gap 22G and O-rings 24, 24 as illustrated inFIG. 1G. When the oil is in the volume as defined it is under pressureand it enters vertical passageway 22A in housing 1 which, in turn,communicates with horizontal passageway 22B in housing 1. Seal 22Sresides in a recess 2Z in cover 2. Recess 2Z is aligned with passageway22B in the housing and communicates, horizontally, with a shortpassageway 2Y in cover 2 which, in turn, communicates with a verticalpassageway 22C in cover 2. Vertical passageway 22C communicates withvolume 22V which is enclosed by front cooler plate 25. Cooler plate 25is affixed to cover 2 with screws 11. As lubricant collects and residesin volume 22V, it passes into and through necked-down area 22D where itis communicated to horizontal passageway 22H. Horizontal passageway 22Hcommunicates opening 22R which provides lubricant to shaft outputspherical bearing 27. Lubrication is provided despite the orientation ofthe gearbox, in other words, if the gear box in inclined, lubricationwill continue by virtue of the just-described pumping system.

Referring to FIGS. 4, 4A and 4B, a gearbox, comprising a housing and afloating gear means for protecting a gear mechanism from damage due toaxial and radial forces applied to the gearbox is disclosed. A firstcooling compartment and a second cooling compartment are disclosed. Thefirst and second cooling compartments are isolated from the floatinggear means. First and second ports supply cooling fluid to the firstcompartment, and, the third and fourth ports supplying cooling fluid tothe second compartment. The ports are all identified with the referencenumeral 38 in FIG. 4.

It is not possible for cooling water to leak into the gearbox as thegearboxes are sealed with respect to the cooling compartments. Water inthe cooling cavities/compartments 12C, 25C is isolated from the gearboxby a thick, heat conductible, wall of steel 12W, 25W, respectively.Cooling cavities/compartments 12C, 25C exist at each end of the gearbox,behind the rear plate 12 and the front plate 25.

FIG. 4 is a top view 400 of the gearbox 9 illustrating cooling waterplugs 38, 38 for the supply of cooling water at the ends of the gearbox.FIG. 4 also illustrates the input shafts 2B, 2B, cover plate 12, coverplate 25, and the output shaft spline 28S. FIG. 4A is the right end view400A of the gearbox with the cooling water plate removed illustratingthe water cavity 12C, the water inlet 12I, the water outlet 12O, and thewall 12W separating the water cavity 12C from the gear systems. Wall 12Wis highly thermally conductive. FIG. 4B is the left end view 400B of thegearbox 9 with the cooling water plate 25 removed illustrating the watercavity 25C, the water inlet 25I, the water outlet 25O, and a wall 25Wseparating the water cavity 25C from the gear systems. Wall 25W is alsohighly thermally conductive. Large amounts of power flow through thegearbox and heat is generated through friction of the gear systems.Referring to FIG. 4, plugs 37, 37 are illustrated sealing the oillubrication drill holes created in the manufacturing process. Plugs 37,37 are also illustrated in FIGS. 3 and 3A.

Cooling cavities 12C, 25C exist at each end of the gearbox, behind plate12 and plate 25, respectively. A portion of cavity 25C is viewable inFIG. 1F. FIG. 4 is a top view 400 of gearbox 9. Plugs 38 are illustratedand they are removed from threaded holes, and hoses are attached tothose holes in order that cooling water be pumped into the cavities. Thecooling water within the cavities 12C, 25C removes heat generated in thegearbox. Cavities 12C, 25C are completely sealed from the gear systemswhich reside behind walls 12W, 25W, respectively.

There is a water conduit that passes through the central portion of thegearbox. When the gearbox is installed in an earth-boring machine, thewater conduit 6C carrying cooling fluid is installed which passesthrough this tube and feeds water to the cutter head. In FIGS. 1 and 1A,reference numeral 6C is used to denote the water conduit 6C through thegearbox 9 and the cutter head 3. Water conduit 6C resides within tube 21as illustrated in FIG. 1F.

Reference Numerals

1-housing

2-cover

2A-input gear

2B-input shaft

2C-cylindrical bushing

2E, 2G, 14, 24-O-ring

2F-screw/connector affixing input shaft 2 b to input gear 2A

2I-internal spline of input gear 2A

2P-external spline of input shaft 2B

2R-receptacle for input shaft 2B

2S-shoulder for retaining bearing

2X-plurality of screws affixing cover 2 to housing 1

2Z-recess in cover in which seal 22S resides

3-cutter head

3A-intermediate gear

3B-splined shaft

3C-shaft input spherical bearing between tube 21 and shaft 3B

3E-sun gear

3F-retaing ring

4-horizontal force acting on the cutter head 3

4A-first planet carrier

4B-first planet gears

4C-first pair of spherical bearings between first planet shaft 4D andfirst planet gear 4B

4D-first planet shafts

5-vertical force acting on the cutter head 3

5A-second planet carrier

5B-second planet gears

5C-second pair of spherical bearings

5D-second planet shafts

6-drive shaft

6A-coupling frame

6B-coupling

6C-water conduit for cooling and lubricating cutting head

7-electric motor, prime mover, one of two

7A-motor frame

7R-roadheader assembly

8-coupling between motor and input gear

9-gearbox

10-bearing cover

11-headed screw

12-rear cooler plate/cap

12S-connector for cooler plate/cap 12

13-adapter

13A-connector/screw

17-planet shaft retainer

20-second sun having a gear and an external spline

21-tube

22-ring gear

22B-horizontal passageway in housing 1

22C-vertical passageway in cover 2

22D-necked down area in cover 2

22G-gap between ring gear 22 and housing 1

22H-horizontal passageway in cover 2 in communication with opening 22 r

22P-port leading to vertical passageway 22A

22R-opening in cover 2 providing lubricant to shaft output sphericalbearing 27

22V-volume in cover 2 in which lubricant resides

22Y-short horizontal passageway in cover 2

22Z-exterior surface of ring gear 22

24R-recess for O-ring

25-front cooler plate/cap

26-dowel pin

27-shaft output spherical bearing

27I-inner race

27O-outer race

27R-rollers

28-output shaft

28L-shoulder on shaft 28

28S-spline on the output shaft

30-bearing cover

30S-connector/screw

31-lip seal

33-lip seal

34, 48, 49-bearing

36-retainer

37-plug in housing

38-port plug in housing which is removed for cooling water connections

38T-threaded connection for cooling water

39-port plug in housing for the addition of oil to the gearbox 9

40-seal

41-dowel pins aligning cover 2 with respect to housing 1

48B-shoulder

48S-input gear shoulder

49S-housing shoulder

51-external spline of spline shaft 3 b meshing with spline 52 of firstsun 3E

52-internal spline of first sun 3E

53-external spline meshing with internal spline 54 of intermediate gear3A

54-internal spline of intermediate gear 3A

55-first planet gear teeth

56-internal ring gear mating with planet gear teeth 55 of first planetgear 4B

57-internal ring gear mating with planet teeth 58 of second planet gear5B

58-second planet gear teeth

59-external spline of the cover 2

60-internal spline of the ring gear 20

61-retaining ring which retains output shaft 28

65-external spline of output shaft 28

66-internal spline of second planet carrier 5A

67-internal spline of first planet carrier 4A

68-external spline of second sun 20

69-external gear of second sun 20

69A-output teeth of the second sun 20

70-teeth of second planet gear 5B

71-inner race of spherical bearing 5C

72-roller bearings of spherical bearing 5C

73-outer race of spherical bearing 5C

74-inner race of spherical bearing 4C

75-roller of spherical bearing 4C

76-outer race of spherical bearing 4C

77-inner race of shaft input spherical bearing 3C

78-roller of shaft input spherical bearing 3C

79-outer race of shaft input spherical bearing 3C

80-shaft seal between second carrier 5A and cover 2

81-stepped bore in input shaft 2B

81A-first shoulder in bore of input shaft 2B

81B-second shoulder in bore of input shaft 2B

82C-outer portion of the input shaft 2B

82D-inner portion of the input shaft 2B

82H-outer shoulder on input shaft 2A

82F-annular groove, fused portion

82R-thin section between annular groove and the stepped bore 81 in inputshaft 2B

82Z-chamfer on shoulder 82H

84-teeth of input gear 2A

85-teeth of intermediate gear 3A

86-bore in receptacle portion 2R of input gear 2A

86A-first shoulder in bore 86 engaging shoulder 82H of input shaft 2B

86B-second shoulder in bore 85 engaging bushing 2C

95A-gap between internal angular spline and external angular spline

96A-gap between internal angular spline and external angular spline

97A-gap, backlash, between internal angular spline and external angularspline

95I-gap between internal involute spline and external involute spline

96I-gap between internal involute spline and external involute spline

97I-gap, backlash, between internal involute spline and externalinvolute spline

99-arrow indicating relative rotation of ring gear 22, housing 1, andsecond planet gears 5B

99A-arrow indicating relative rotation of second planet gear 5B andsecond sun 20

99B-arrow indicating relative rotation of first sun gear 3E and splinedshaft 3B

99C-arrow indicating relative rotation of intermediate gear 3A andspline shaft 3B

99D-arrow indicating relative rotation of second carrier 5A and outputshaft 28

99E-arrow indicating relative rotation of first planet gear 4B, ringgear 20 and housing 1

99Z-arrow indicating rotation of the roadheader

100-schematic view of a roadheader including the cutter head, gearboxand prime mover

100A-enlarged portion of the schematic view of FIG. 1 illustrating thecutter head and gearbox

100B-perspective view of the gearbox

100C-front view of the gearbox

100D-right side view of the gearbox where power is input to the gearbox

100E-left side view of the gearbox where power is output from thegearbox.

100F-cross-sectional view taken along the lines 1F-1F of FIG. 1Dillustrating the first planetary gear system, the second planetary gearsystem, the floating ring gear, the input to the first planetary gearsystem, and the output from the second planetary gear system, all ofwhich are supported by shaft input and output spherical bearingsenabling the gear systems and ring gear to float within a fixed housing

100G-enlarged portion of the cross-sectional view of FIG. 1Fillustrating the floating ring gear, the spline connection between thefloating ring gear and the cover, and a portion of the lubricationsystem

100H-enlarged portion of the cross-sectional view of FIG. 1Fillustrating the spline input to the first sun driving the firstplanetary gear set, the first planet carrier driving the second sun, thesecond sun driving the second planetary gear set and the second planetcarrier driving the output spindle, all of which are supported by theshaft input and output spherical bearings enabling the gear systems andring gear to float within a fixed housing

100I-enlarged portion of the cross-sectional view of FIG. 1Fillustrating a shaft input spherical bearing interposed between thecentrally located support tube and the splined shaft driven by theintermediate gear

100J-perspective view of the floating gearbox without the ring gear andwithout the housing

100K-perspective view of the floating gearbox with the ring gear shownin an exploded position

100L-diagrammatic view of an angular spline

100M-diagrammatic view of an involute spline

200-cross-sectional view taken along the lines 2-2 of FIG. 1Dillustrating the fused input shaft with a splined connection to theinput gear which drives the intermediate gear which in turn drives thesplined shaft

200A-a front view of the input gear

200B-cross-sectional view of the input gear illustrating the internalspline for connection with the fused input shaft

200C-front view of the fused input shaft

300-cross-section taken along the lines 3-3 of FIG. 1E illustrating thelubrication system and passageways in the ring gear, the housing, andthe cover

300A-enlargement of a portion of FIG. 3 illustrating the lubricantpassages through the cover and housing.

300B-perspective view of a portion of the cover illustrating thelubricant passages through the cover

300C-plan view of the floating ring gear illustrating the lubricantpassageway therethrough

300D-cross-sectional view of the floating ring gear illustrating thelubricant passageway therethrough

400-top view of the gearbox illustrating cooling water plugs

400A-right end view of the gearbox with the cooling water plate removedillustrating the water cavity, the water inlet, the water outlet, and awall separating the water cavity from the gear systems

400B-left end view of the gearbox with the cooling water plate removedillustrating the water cavity, the water inlet, the water outlet, and awall separating the water cavity from the gear systems

TT-tooth thickness

SW-space width

The invention has been set forth by way of example only and thoseskilled in the art will recognize that changes may be made to theexamples provided herein without departing from the spirit and the scopeof the appended claims.

1-6. (canceled)
 7. An overload protection device in combination with aprime mover and gearbox transmission supplying torque through saidgearbox transmission to a load, comprising: an input shaft; said primemover transmitting torque to said input shaft; said gearbox transmissionincludes an input gear; said input shaft affixed to said input gear;said input shaft includes an annular groove; said input gear of saidgearbox transmission drives a planetary gear system which, in tum,supplies power to said load; and, upon overload of said gearboxtransmission, said input shaft breaks at said annular groove.
 8. Anoverload protection device in combination with a prime mover and gearboxtransmission supplying torque through said gearbox transmission to aload, as claimed in claim 7, further comprising: said input gearincludes a bore therein; said bore of said input gear includes aninternal spline; said input shaft includes a bore therethrough; saidinput shaft includes an external spline; and, said external spline ofsaid input shaft engages said internal spline of said input gear.
 9. Anoverload protection device in combination with a prime mover and gearboxtransmission supplying torque through said gearbox transmission to aload, as claimed in claim 7, wherein said annular groove of said inputshaft is U-shaped in cross-section.
 10. An overload protection device incombination with a prime mover and gearbox transmission supplying torquethrough said gearbox transmission to a load, as claimed in claim 7,wherein said annular groove of said input shaft is thin incross-section.
 11. An overload protection device in combination with aprime mover and gearbox transmission supplying torque through saidgearbox transmission to a load, comprising: an input shaft; said inputshaft includes a bore therethrough; said input shaft includes anexternal spline; said prime mover transmitting torque to said inputshaft; said gearbox transmission includes an input gear; said input gearincludes a bore therein; said bore of said input gear includes aninternal spline; said input shaft includes a weakened region; said inputgear of said gearbox transmission drives a planetary gear system which,in tum, supplies power to said load; and, upon overload of said gearboxtransmission, said input shaft breaks at said weakened region.
 12. Anoverload protection device in combination with a prime mover and gearboxtransmission supplying torque through said gearbox transmission to aload, as claimed in claim 11, wherein said weakened region is U-shapedin cross-section.
 13. An overload protection device in combination witha prime mover and gearbox transmission supplying torque through saidgearbox transmission to a load, as claimed in claim 11, wherein saidweakened region is thin in cross-section.
 14. An overload protectiondevice in combination with a prime mover and gearbox transmissionsupplying torque through said gearbox transmission to a load,comprising: an input shaft; said input shaft includes a boretherethrough; said input shaft driven by said prime mover and forrotation therewith; said input shaft includes an external spline and anouter shoulder; said prime mover transmitting torque to said inputshaft; said gearbox transmission includes an input gear; said input gearincludes a receptacle portion, said receptacle portion includes a boretherein; said bore of said receptacle portion of said input gearincludes an internal spline, said bore of said receptacle portion ofsaid input gear includes a first shoulder therein; said input shaftincludes an annular groove; said input gear of said gearbox transmissiondrives a planetary gear system which, in tum, supplies power to saidload; and, upon overload of said gearbox transmission, said input shaftfractures said annular groove and said first shoulder of said receptacleportion of said input gear engages said outer shoulder of said inputshaft preventing said annular groove, once fractured, from movinginwardly toward said input gear preventing damage to said input gear.15. An overload protection device in combination with a prime mover andgearbox transmission supplying torque through said gearbox transmissionto a load, as claimed in claim 14, wherein said annular groove isU-shaped in cross-section.
 16. An overload protection device incombination with a prime mover and gearbox transmission supplying torquethrough said gearbox transmission to a load, as claimed in claim 14,further comprising: said bore of said receptacle portion includes afirst groove and a second groove; a first seal resides in said firstgroove and seals against said input shaft; and, a second seal resides insaid second groove and seals against said input shaft.
 17. An overloadprotection device in combination with a prime mover and gearboxtransmission supplying torque through said gearbox transmission to aload, as claimed in claim 16, further comprising: said first seal andsaid second seal straddle said annular groove and maintain lubricantbetween said first and second seals and between said input shaft andsaid bore of said receptacle portion of said input gear.